Keratitis is one of the leading global causes of ocular morbidity, and it is also an eye disease that may lead to blindness. One source of keratitis may be attributed to fungi infection of the eye. These fungi may include yeast-like fungi such as Candida albicans (C. albicans) or filamentous fungi such as Aspergillus fumigatus and Aspergillus niger (A. niger).
Conventional therapies mainly involve the use of clinical antifungal or antimicrobial drugs which often fall short of their effectiveness due to various reasons.
Fungal keratitis infection often exists as a biofilm, which is particularly difficult to clear because of its encasement in a protective and impermeable extracellular matrix. Therefore, a much higher dosage of antimicrobials is needed for fungi biofilm clearance as compared to planktonic microbial substrates.
Another reason for the ineffectiveness of conventional therapies is due to the shortage of broad-spectrum efficient antifungal drugs. Current clinical drugs for treating fungal keratitis may comprise either azole compounds or polyenes. Examples may include fluconazole and amphotericin B respectively as shown below.

The fungistatic nature of azole compounds, which function via enzyme inhibition, requires a prolonged course of application. Moreover, azoles are extremely unstable such that their topical solutions must be stored at low temperatures and protected from light.
On the other hand, polyenes, which function via disrupting the permeability of ions through the cell membrane, are expensive.
Notably, the above clinical drugs exhibit poor penetration, solubility and stability which limit their application for fungal keratitis treatment. These limitations, together with the development of drug resistance, have further led to the low efficacy and unsatisfactory outcome associated with the current therapies for fungal keratitis.
To mitigate the above limitations and the growing health threat posed by resistant pathogenic microorganisms, further developments of antibiotics with new mechanisms of action, including peptides and synthetic polymers, have attracted considerable research interests. Amphiphilic peptides (AMP) or synthetic polymers have unique killing mechanism that may slow down the development of drug resistance. However, no antifungal properties have been observed for these new materials.
A more recent development includes the use of imidazolium salts (IMSs) as clinical drugs. However, these biocidal IMSs usually have very low selectivity, minimal hemolytic concentration (represented as MHC or MIC), usually in the range of 1.25-5, which excludes them from their potential systemic usage.
Accordingly, there is a need to provide an antifungal drug that overcomes, or at least ameliorates, one or more of the disadvantages described above.
There is also a need to provide an effective therapy for the treatment of keratitis that overcomes, or at least ameliorates, one or more of the disadvantages described above.